The monitoring of arterial blood gases is essential for the management of any sick infant, but is especially important in vulnerable, extremely premature infants where even a minimal delay in appropriate interventions can be the difference between life and death. Intermittent monitoring of blood gases, as is traditionally performed, provides only a spot check of the physio-pathological status of the patient; the results are often delayed from the actual event triggering blood gas analysis, and the procedure, besides predisposing to iatrogenic infections, in itself is painful and, over time, can result in significat blood loss. Continuous and non-invasive monitoring is preferable for monitoring blood gases, but current non-invasive continuous modalities have significant limitations. This has led to several attempts to develop a non-invasive and continuous blood gas monitoring system, but without success, and at present no commercially available system exists that fulfills the accuracy, precision, and safety needs of a continuous blood gas monitoring system. An accurate, precise, and intrinsically safe system that exploits routinely performed intravascular catheterization (such as umbilical artery catheterization - the standard of care for sick neonates) to obtain blood gas measurements continuously would be an important advance in monitoring critically ill neonates admitted to NICUs. To address this need, we propose to develop an integrated fiber optic sensor umbilical (ISUM) catheter for blood gas monitoring in neonates. The ISUM catheter will fill the technological gap in continuous blood analysis by addressing the deficiencies shown in classical intravascular sensor probes, and will take advantage of the fact that most newborns in NICUs receive at least one intravascular catheter, with umbilical arterial catheterization being one of the most commonly performed procedures. The sensor and the catheter will be designed as an integrated unit for this specific application, and will have the following advantages over previously described intravascular probes: (1) large area gas sensors, eliminating the probe placement or movement artifacts; (2) dual oxygen sensor and data fusion, improving reliability; (3) placement of the integrated sensor catheter in a central artery will eliminate vessel spasms; (4) calibration-free sensors, with no with no delay in data acquisition time; and (5) reduced cost, since highly repeatable sensor elements can be produced in batches of hundreds. Completion of the proposed aims will result in a validated ISUM catheter ready for human subject testing. As soon as the milestones proposed in this application are achieved, we will move quickly to commercialize the ISUM catheter by 1) applying for Phase II funding for clinical trials; 2) starting the process for an FDA 510 (k) submission; 3) approaching investors for commercialization.